The cleaning of skin with surface-active cleansing preparations is the basis for the personal cleansing consumer market world-wide. Many people wash their skin with various surface-active preparations several times a day, with frequent whole body exposure to these compositions (e.g. bathing or showering). Traditionally, consumers were offered these cleansing compositions in the form of a solid "bar" comprised of either alkali earth salts of fatty acids (soap) or mixed synthetic surfactant/soap systems. While these products provide acceptable cleansing of skin and performance properties (e.g. lather), they possess certain properties which give rise to specific consumer negatives in terms of product messiness during use and irritation to skin (e.g. drying). These specific consumer negatives have been partially addressed through the introduction of liquid personal cleanser compositions in the form of shower gels. However, these shower gel products while addressing messiness and mildness needs of the consumer, often fail to meet other consumer performance needs, specifically high lather and soap-like rinse feel. A shower gel composition delivering high mildness, high lather, and rinsing properties more soap-like would be very desirable.
Skin cleansing compositions should lather and rinse, cleanse the skin gently, causing little or no irritation, without drying the skin after frequent routine use. Certain synthetic surfactants and surfactant systems formulated for skin cleansing are particularly mild, however, they possess poor lather performance and slick rinse-feel attributes. Other surfactants and surfactant systems (for example, soap-based system) provide good lather and rinsing performance, but are not exceptionally mild to the skin. Additionally, these formulations require a thickening agent, often some polymeric component, along with high levels of salt to produce consumer acceptable product viscosities. This thickening approach can cause the product to exhibit dramatic viscoelastic properties during use and impact other product performance attributes (e.g. ease of lathering). In addition, polymeric thickeners can be costly and exhibit base odors.
Optimization of any single product attribute (e.g. lather, mildness, rinse feel, viscosity), is a relatively straightforward process. There are numerous combinations of surfactants and other components which can be utilized to generate a product which delivers against any of the aforementioned attributes. The use of known high sudsing anionic surfactants with lather boosters yields acceptable lather volume. Unfortunately, highest sudsing anionic surfactants are, generally, also highest in skin irritation and, hence, worst in clinical mildness. Surfactants that are among the mildest with minimal skin irritation, such as ammonium lauryl ether (12EO) sulfate (NH4AE12S) are extremely poor in lather. These two facts alone make the selection of surfactants for optimization of lather performance, in and of itself, a delicate balancing act and becomes even more complex when the other product attributes must be optimized as well. See, e.g., U.S. Pat. Nos. 4,338,211, Stiros, issued Jul. 6, 1982; 4,310,433, Stiros, issued Jan. 12, 1982; and 4,842,850, Vu, issued Jun. 27, 1989, all of said patents being incorporated herein by reference.
In short, mildness is often obtained at the expense of effective cleansing and lathering. In addition, these mild formulations often come at the expense of other consumer preferred product performance attribute, such as bar soap-like rinse feel Finally, the thickening of these mild formulations also results in product viscoelastic properties which are non-ideal.